Coat colour E locus e^a / chestnut (MC1R-related) - Belgian Draft

What does this test analyse?

This genetic test detects the MC1Re^a allele with variant c.250G>A. In horse breeding this trait is known as the E locus, extension, red factor, chestnut, sorrel or red base colour. In Belgian Draft horses, this is a recognised E-locus variant that determines whether black pigment can be expressed in the coat.

The E locus controls the balance between black pigment and red/yellow pigment. A functional E allele allows black pigment, while the recessive e^a allele restricts black pigment formation. A horse with two e^a copies therefore has the genetic basis for chestnut/red coat colour. Other coat-colour genes can still influence the final shade, intensity or dilution.

Practical value of this test

• The test helps breeders estimate whether a mating can produce chestnut foals in lines where the e^a allele occurs.
• A non-chestnut horse can still be a carrier; the DNA result reveals hidden carriers.
• For colour planning, the result can be combined with A locus, Cream, Pearl, Champagne, Dun, Silver and other coat-colour tests.
• The result supports more targeted mare and stallion choices when base colour, registration colour or colour expectation has commercial value.
• For sales and communication with owners, the test gives more certainty than appearance or pedigree alone.

Inheritance and result

The e^a allele is autosomal recessive. E/E means that the tested e^a variant was not detected. E/e^a means that the horse carries one copy and can pass the allele on. e^a/e^a causes chestnut/red base colour for this variant. If other E-locus variants are relevant in a line, combining this result with additional colour information gives the most complete prediction.